1. Field of the Invention
The present invention relates generally to improvement of noise, vibration and harshness (NVH) characteristics for vehicles while maintaining excellent handling and steering, and in particular, to improvement of NVH characteristics by selective placement of active vibration dampers to cancel noise from the road.
2. Discussion of the Prior Art
The bushings and other interfaces between a vehicle body and suspension or body and frame in a vehicle suspension system strongly influence the vehicle""s steering and handling performance, as well as its interior noise, vibration and harshness (NVH) characteristics. For example, if the bushings are relatively stiff, then the vehicle will have good steering and handling performance but poor NVH properties. On the other hand, if the bushings are relatively soft, then poor steering and handling results, but the vehicle has good interior NVH characteristics. Hence, good steering, handling and good NVH qualities have not been truly achieved for a vehicle, because of this adversarial relationship.
Active materials are materials that either actuate or sense when a stimulus is applied. Piezoelectrics are active materials that extend and contract when an electric field is applied, thereby acting as an actuator. In addition to being used as an actuator, piezoelectrics are used as sensors that emit a voltage when mechanically loaded. Magnetostrictives are active materials that extend in the presence of a magnetic field. Other active materials include magnetic shaped memory alloys that extend, bend, twist or contract when a magnetic field is applied.
Piezoelectric materials have been used in automobiles and airplanes for vibration absorption and noise suppression, in particular, in association with the engine. Unfortunately, known uses of piezoelectric materials in automobiles and other vehicles do not reduce noise transmitted to the interior of a vehicle through the bushings and other interfaces between the suspension and body or body and frame.
Therefore a need exists for a method and apparatus for improved steering, handling and NVH characteristics of a vehicle.
Accordingly, an object of the present invention is to provide an apparatus and method that provides improved NVH characteristics in a vehicle while providing excellent steering and handling.
Another object of the present invention is to selectively place vibration dampers such that steering, handling and NVH characteristics are improved in a vehicle.
In accordance with the invention, a noise reduction apparatus for a vehicle is provided. The noise reduction apparatus includes a vehicle suspension component adapted to be attached to one of a vehicle frame and a vehicle body. The vehicle suspension component, for example, a bushing of a control arm of a vehicle suspension, has a first characteristic that increases the vehicle steering, ride or handling capabilities. The vehicle suspension component has a second characteristic that increases the noise, vibration and harshness of the vehicle. The noise reduction apparatus includes an active vibration damper that counters noise, vibration and harshness from said vehicle suspension component. The active vibration damper preferably includes a piezoelectric component, a magnetostrictive component or a magnetic shaped alloy, excited in response to, and in a manner to counter, vibrations from the road.
A method in accordance with the invention includes providing a vehicle suspension component that affects noise, vibration, harshness, steering and handling. The vehicle suspension component is attached to a vehicle body or frame. An active vibration damper in accordance with the invention is placed at the interface between the vehicle suspension component and the body or frame.